San Juan (SJU) to Boston (BOS): On-Time Performance
Data through May 2026
The calendar drives reliability on SJU–BOS. June 2025 flights landed on schedule 85% of the time, but January 2026 dropped to 64% — a gap of 22 points. Across the full period the route averages 73% on-time against a national 78%. Morning departures also hold up better than evening ones (80% vs 62%), which matters most in the rough months.
- On-time
- 73%
- arrived <15 min late
- Avg delay
- 22 min
- completed flights
- Cancelled
- 1.9%
- Flights/day
- 5.6
- last 12 months
- Duration
- 4h 13m
- scheduled
- Distance
- 1,674 mi
Best airline from SJU to BOS
4 airlines flew this route regularly between 2024-06 and 2026-05.
| Airline | On-time | Avg delay | Cancelled | Flights |
|---|---|---|---|---|
| Delta Air Linesmost reliable | 81% | 16 min | 1.4% | 797 |
| Spirit Airlines | 78% | 14 min | 4.1% | 317 |
| Frontier Airlines | 71% | 16 min | 1.7% | 241 |
| JetBlue Airways | 71% | 24 min | 1.8% | 2,976 |
Monthly on-time trend
Best time to fly from SJU to BOS
Aim for departures around 12 a.m. (94% on-time); avoid 10 p.m. departures (49%).
By day of week
| Day | On-time | Avg delay |
|---|---|---|
| Monday | 73% | 23 min |
| Tuesdaybest | 78% | 17 min |
| Wednesday | 74% | 18 min |
| Thursday | 72% | 22 min |
| Friday | 74% | 19 min |
| Saturday | 71% | 27 min |
| Sunday | 71% | 23 min |
What causes delays on this route
Share of total delay minutes by cause, as reported by carriers to the US DOT.
- Late-arriving aircraft41%
- Airline operations38%
- National airspace system19%
- Weather2%
Frequently asked questions
- How often are flights from SJU to BOS delayed?
- 27% of SJU–BOS flights arrived 15 or more minutes late (the US DOT definition of a delay) between 2024-06 and 2026-05. The average arrival delay across completed flights was 22 minutes.
- Which airline is most reliable from SJU to BOS?
- Delta Air Lines has the best on-time record on this route at 81%, based on 797 flights. 4 airlines flew SJU–BOS frequently enough to compare in this period.
- What is the best time of day to fly from SJU to BOS?
- Departures around 12 a.m. have the best record (94% on-time), while departures around 10 p.m. have the worst (49%). As on most US routes, delays accumulate through the day, so earlier flights are generally safer.
- How long is the flight from SJU to BOS?
- The scheduled SJU–BOS flight time averages 4h 13m over 1,674 miles. Actual arrival times vary — flights on this route land 15+ minutes late 27% of the time.
- How often are SJU to BOS flights cancelled?
- 1.9% of scheduled flights on this route were cancelled between 2024-06 and 2026-05, slightly above the national rate of 1.6%.
- What is the worst month to fly from SJU to BOS?
- January 2026 was the roughest month in this dataset, with only 64% of arrivals on time. The best was June 2025 at 85%. If your dates are flexible, that 22-point gap is worth planning around.
Explore related pages
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Based on 4,331 flights, 2024-06–2026-05. Source: US DOT Bureau of Transportation Statistics. Updated 2026-07-01.